1. Field of the Invention
This invention relates to a malfunction protection system for use in automatic meter reading systems or the like and more particularly to a system for protecting against malfunctions due to tampering or other causes and which highly reliable and trouble-free in operation while being comparatively simple in construction and operation. The protection system of the invention is particularly advantageous in a system which uses customer telephone lines for reporting of meter data.
2. Background of the Prior Art
Many systems have been used or proposed in the prior art for automatic transmission of meter data to a remote location, many of which use telephone lines for automatic reporting of meter and status data. In many of such systems, an interrogation signal is sent through telephone lines from a receiving station to a reporting station to initiate the sending of a report, the receiving station being either at a telephone exchange or being connected through a telephone line thereto. Such systems may involve ringing of the customer's telephone or the installation of special ring-suppress equipment at the customer's facility or, alternatively, special equipment at the telephone exchange. In another type of system, a reporting station initiates the making of a report.
Such systems may be subject to malfunctions from various causes. For example, in systems such as those designed for monitoring water, gas or electric consumption at a residential or commercial location, there is a possibility of tampering with the equipment in an attempt to prevent transmission of accurate data to a utility. This possibility has been recognized and dealt with in the prior art but it is found that the prior art systems have not been as reliable as would be desirable.